1|Page
BIOL 1108 SPRINGTHORPE UGA - EXAM 3 2025
| COMPREHENSIVE Q&A FOR GUARANTEED
SUCCESS
Stomata - correct-answer-gaps in the leaf that open and close using guard cells
Open - water vapor escapes
Closed - water stays in leaves
How water vapor enters leaves - correct-answer-•As water vapor escapes out the
stomata, a tiny vacuum is created (negative pressure)
•Pressure also moves from high to low
•High pressure H2O in xylem is drawn to the low pressure in the leaves
Negative vs Positive Pressure - correct-answer-Negative pressure is responsible for
water being drawn up to the leaves
Pulling up creates negative pressure, forcing the liquid to move up into the syringe
where there is low pressure.
Pushing down creates positive pressure by increasing the pressure in the syringe,
forcing liquid out.
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Stomata primary function - correct-answer-gas exchange
What gases do plants need? - correct-answer-Plants need CO2 for photosynthesis
What gases do they need to get rid of? - correct-answer-O2, can be toxic in high
amounts to plants
What do they lose by accident? - correct-answer-Water Vapor (H2O)
Photosynthesis Equation (Balanced) - correct-answer-6CO2 + 6H2O ------>
C6H12O6 + 6O2
Constant gas exchange would be ideal (Why?) - correct-answer-To maximize
photosynthesis, plants would like to constantly be exchanging O2 for CO2 by
leaving their stomata open.
•Tradeoff: water loss for CO2/O2 gas exchange
How is gas exchange controlled - correct-answer-Physical process of opening and
closing stomata
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How Stomata Work - correct-answer-•Open - (guard cells turgid) when water is
abundant
•Close (guard cells flaccid) when water is scarce.
•Backup: Can force stomata to open using hormones and ion flow
How water effects Stomata - correct-answer-1)When water is abundant in the
environment, all the plant's cells are turgid because of osmosis, including guard
cells. When this is true, these cells create an opening between them . This means
as long as there's a lot of water, stomata stay open for gas exchange.
2)However, when water starts to run out, the cells turn flaccid. When that
happens to guard cells, they "deflate' and seal up the gap between them, closing
the stomata. In this way, if there is a danger of running out of water, stomata seal
up, preventing further water loss.
This also limits the plant's ability to photosynthesize until there's again enough
water.
Total Amount of Water Transpired? - correct-answer-depends on the amt. of time
stomata are open and rate
•Ex. On a hot, dry, windy day, a plant with closed stomata won't lose ANY water
BIOL 1108 SPRINGTHORPE UGA - EXAM 3 2025
| COMPREHENSIVE Q&A FOR GUARANTEED
SUCCESS
Stomata - correct-answer-gaps in the leaf that open and close using guard cells
Open - water vapor escapes
Closed - water stays in leaves
How water vapor enters leaves - correct-answer-•As water vapor escapes out the
stomata, a tiny vacuum is created (negative pressure)
•Pressure also moves from high to low
•High pressure H2O in xylem is drawn to the low pressure in the leaves
Negative vs Positive Pressure - correct-answer-Negative pressure is responsible for
water being drawn up to the leaves
Pulling up creates negative pressure, forcing the liquid to move up into the syringe
where there is low pressure.
Pushing down creates positive pressure by increasing the pressure in the syringe,
forcing liquid out.
,2|Page
Stomata primary function - correct-answer-gas exchange
What gases do plants need? - correct-answer-Plants need CO2 for photosynthesis
What gases do they need to get rid of? - correct-answer-O2, can be toxic in high
amounts to plants
What do they lose by accident? - correct-answer-Water Vapor (H2O)
Photosynthesis Equation (Balanced) - correct-answer-6CO2 + 6H2O ------>
C6H12O6 + 6O2
Constant gas exchange would be ideal (Why?) - correct-answer-To maximize
photosynthesis, plants would like to constantly be exchanging O2 for CO2 by
leaving their stomata open.
•Tradeoff: water loss for CO2/O2 gas exchange
How is gas exchange controlled - correct-answer-Physical process of opening and
closing stomata
, 3|Page
How Stomata Work - correct-answer-•Open - (guard cells turgid) when water is
abundant
•Close (guard cells flaccid) when water is scarce.
•Backup: Can force stomata to open using hormones and ion flow
How water effects Stomata - correct-answer-1)When water is abundant in the
environment, all the plant's cells are turgid because of osmosis, including guard
cells. When this is true, these cells create an opening between them . This means
as long as there's a lot of water, stomata stay open for gas exchange.
2)However, when water starts to run out, the cells turn flaccid. When that
happens to guard cells, they "deflate' and seal up the gap between them, closing
the stomata. In this way, if there is a danger of running out of water, stomata seal
up, preventing further water loss.
This also limits the plant's ability to photosynthesize until there's again enough
water.
Total Amount of Water Transpired? - correct-answer-depends on the amt. of time
stomata are open and rate
•Ex. On a hot, dry, windy day, a plant with closed stomata won't lose ANY water
